Seaweed bioplastic

Bio-based plastics produced from seaweed have the potential to replace conventional plastics in many applications, in particular packaging. Cast as transparent films, they offer a renewable and compostable alternative to plastics such as polypropylene (PP), polyethylene (PE) and polyethylene terephthalate (PET), polyester.

Seaweed-based biopolymers include alginate, agar and carrageenan. These are polysaccharides made up of sugar molecules bonded together in long chains. There are many types of seaweed and several of them are suitable for bioplastic production. Each has its own qualities and benefits, such as providing an effective barrier, water solubility, printability, or thermoplastic properties.

As well as providing raw materials for bio-based plastics, they are used as thickeners, gelling agents and stabilisers in cosmetics and food products. Indeed, it is possible to make edible bioplastics from these ingredients.

Since it is not in full-scale commercial production, the environmental impact is not yet a complete picture. Seaweed as a feedstock has a lot of upsides: they are easily cultivated in natural environments without fertiliser, do not compete with food sources, are able to grow in a wide range of environments, present no risk to potential deforestation, and sequester carbon.

The energy intensive parts of the process are the drying and processing of the seaweed, and the formation of the product, such as film casting. In any case, the carbon footprint is likely to reduce once production becomes established, and there is even the possibility of becoming carbon neutral, as some of the manufactures already boldly claim, if the sequestrated CO2 is taken into account.

The only major drawback of these materials is cost. While the production processes are still largely manual, such as cultivating the seaweed, production has not yet scaled up to compete with conventional plastics.

As with edible seaweed, there is a risk that undesirable contaminants that have accumulated in the marine environment as a result of human activity end up in seaweed plastic. Risks include arsenic, cadmium, mercury, lead, iodine, kainic acid, biotoxins, anti-nutrients, persistent organic pollutants, microplastic and radionuclides. There is very little legislation in this area, partly because it is still small-scale and developing fast.